From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: kkabe@vega.pgw.jp, bhe@redhat.com, david@redhat.com,
osalvador@suse.de, bugzilla-daemon@bugzilla.kernel.org,
richardw.yang@linux.intel.com, n-horiguchi@ah.jp.nec.com,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH] memory_hotplug: disable the functionality for 32b (was: Re: [Bug 206401] kernel panic on Hyper-V after 5 minutes due to) memory hot-add
Date: Wed, 19 Feb 2020 13:46:45 -0800 [thread overview]
Message-ID: <20200219134645.7430db57e0e59f69e7386f46@linux-foundation.org> (raw)
In-Reply-To: <20200218100532.GA4151@dhcp22.suse.cz>
On Tue, 18 Feb 2020 11:05:32 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> Subject: [PATCH] memory_hotplug: disable the functionality for 32b
>
> Memory hotlug is broken for 32b systems at least since c6f03e2903c9
> ("mm, memory_hotplug: remove zone restrictions") which has considerably
> reworked how can be memory associated with movable/kernel zones. The
> same is not really trivial to achieve in 32b where only lowmem is the
> kernel zone. While we can tweak this immediate problem around there are
> likely other land mines hidden at other places.
>
> It is also quite dubious that there is a real usecase for the memory
> hotplug on 32b in the first place. Low memory is just too small to be
> hotplugable (for hot add) and generally unusable for hotremove. Adding
> more memory to highmem is also dubious because it would increase the
> low mem or vmalloc space pressure for memmaps.
>
> Restrict the functionality to 64b systems. This will help future
> development to focus on usecases that have real life application. We
> can remove this restriction in future in presence of a real life usecase
> of course but until then make it explicit that hotplug on 32b is broken
> and requires a non trivial amount of work to fix.
(cc linux-arch)
(and linux-arm-kernel, as ARM is a major 32-bit user)
Does anyone see a problem with disabling memory hotplug on 32-bit builds?
next prev parent reply other threads:[~2020-02-19 21:46 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-206401-27@https.bugzilla.kernel.org/>
[not found] ` <bug-206401-27-zYD8WfDKqD@https.bugzilla.kernel.org/>
2020-02-10 5:32 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes due to memory hot-add Andrew Morton
2020-02-10 5:40 ` Baoquan He
2020-02-10 5:56 ` Andrew Morton
2020-02-10 6:09 ` Baoquan He
2020-02-10 6:15 ` Baoquan He
2020-02-10 23:07 ` Wei Yang
2020-02-12 0:41 ` Andrew Morton
2020-02-12 7:31 ` Baoquan He
2020-02-12 8:21 ` David Hildenbrand
2020-02-13 4:22 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes due tomemory hot-add kabe
2020-02-13 8:19 ` Baoquan He
2020-02-14 14:26 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes duetomemory hot-add kkabe
2020-02-14 14:48 ` Baoquan He
2020-02-14 15:01 ` Baoquan He
2020-02-17 4:48 ` Baoquan He
2020-02-17 5:31 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes duetomemoryhot-add kkabe
2020-02-17 8:00 ` David Hildenbrand
2020-02-17 10:33 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes duetomemory hot-add Michal Hocko
2020-02-17 11:21 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes due to memory hot-add kkabe
2020-02-17 5:46 ` kkabe
2020-02-17 7:44 ` Baoquan He
2020-02-17 9:34 ` Oscar Salvador
2020-02-17 10:13 ` Baoquan He
2020-02-17 10:17 ` Baoquan He
2020-02-17 10:24 ` David Hildenbrand
2020-02-17 10:33 ` Baoquan He
2020-02-17 10:38 ` David Hildenbrand
2020-02-17 11:20 ` Baoquan He
2020-02-17 12:47 ` Michal Hocko
2020-02-18 6:24 ` kkabe
2020-02-18 8:47 ` Michal Hocko
2020-02-18 9:19 ` kkabe
2020-02-18 9:26 ` David Hildenbrand
2020-02-18 10:05 ` [RFC PATCH] memory_hotplug: disable the functionality for 32b (was: Re: [Bug 206401] kernel panic on Hyper-V after 5 minutes due to) " Michal Hocko
2020-02-18 10:11 ` David Hildenbrand
2020-02-19 3:23 ` Baoquan He
2020-02-19 21:46 ` Andrew Morton [this message]
2020-02-19 23:07 ` [RFC PATCH] memory_hotplug: disable the functionality for 32b Robin Murphy
2020-02-19 3:39 ` [Bug 206401] kernel panic on Hyper-V after 5 minutes due to memory hot-add Baoquan He
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